A man has been released on police bail after his arrest in connection with a motorway crash that left two men dead and six other people injured.

The 25-year-old-man, from east London, was arrested on suspicion of causing death by dangerous driving after a collision involving two BMWs on the M1 near Watford in Hertfordshire.

The driver and rear seat passengers of one of the cars were killed in the crash, which happened just before 2.40am on Monday.

The two dead have been named by police as Gulzar Ahmed, 22, and Mohammed (Mizanur) Rahman, 24, both from east London.

Tributes have been paid to the young men.

Friends took to Twitter, with @Sabah--ChotuAFC writing: "R.I.P Mizanur & Gulzar, from E.london, died on the M1 in a race where they were driving at 140mph. Thoughts & prayers with their families."

Another tweeter, @Miraz--U, wrote: "R.I.P Mizanur & Guljar. Died in a car crash on the M1 driving at 140mph."

A relative of one of the other men involved in the crash told the Evening Standard: "They (Mizanur and Guljar) were lovely guys and good family men. We are all very upset.

"Mizanur had a baby daughter and this is a terrible thing that has happened."

The men who died were the driver and a rear seat passenger of one of the cars, Hertfordshire Police said.

Six other people were taken to hospital for treatment following the crash.

Witnesses have said the two cars "appeared to be having a high-speed race."

Basit Nasir told the Evening Standard that the BMWs had sped past him at around 140mph.

He said: "It was total mayhem. There was mangled metal everywhere. It was foolish of them to drive at this sort of speed. It was raining as well."

Mr Nasir said that four men in a Mercedes arrived at the crash scene and scuffled with survivors.

He told the London newspaper: "They all jumped out and everybody started punching each other. They said, 'What have you done? You have killed them.' I tried to break up the fight and called the police from my mobile."

The accident, which happened between junctions five and four, resulted in the closure of five junctions of the motorway in both directions, and the southbound stretch was shut for several hours.

The 25-year-old man has been released on police bail pending further enquiries.

Inspector Paul Campbell, from Bedfordshire and Hertfordshire Roads Policing Unit, which is investigating the collision, said: "This was a devastating collision which has sadly resulted in two men losing their lives and others being seriously injured.

"Our investigation into the cause of this collision will be in-depth and will take a considerable amount of time. What we do know is that both of the vehicles involved - the two BMWs - have been travelling a number of seconds apart and have, for reasons unknown at this time, separately lost control before eventually colliding with each other.

"A number of contributory factors need to be carefully considered to piece together the precise events."

Hertfordshire Police are appealing for witnesses to the collision or the events leading up to it to contact them on 101.